218
UNIT 3
Organ Systems
CLINICAL CORRELATIONS
Figure 11-16A.
Acute Respiratory Distress Syndrome.
H&E,
3
1,079
Acute respiratory distress syndrome (ARDS)
is a clinical
term describing acute lung injury, correlating with the
pathologic entity of
diffuse alveolar damage
. ARDS is a
respiratory emergency, characterized by an acute onset
of shortness of breath (developing in 4–48 hours), which
progresses to respiratory failure. It is caused by a broad
spectrum of diseases such as
pneumonia
, severe injury to
the lungs, severe trauma, burns,
sepsis
, medications, and
shock. ARDS is not a
speciF
c lung disease, but a spec-
trum of clinical and pathological changes due to acute
lung injury. Pathologic F
ndings depend on the stage of
the condition, and include (1) excess fl
uid in the intersti-
tium and alveoli with rupture of the alveolar structures;
(2) proliferation of type II pneumocytes and squamous
metaplasia and myoF
broblasts inF
ltration; and (3) hya-
line membranes.
Hyaline membranes
consist of F brin and
remnants of necrotic pneumocytes that line the alveo-
lar spaces, as seen in the photomicrograph. Treatment
includes using mechanical ventilation and treating the
underlying disease.
Figure 11-16B.
Emphysema.
H&E,
3
27
Chronic obstructive pulmonary disease (COPD)
includes
emphysema
and
chronic bronchitis
. Emphysema is
characterized by the permanent destruction of alveolar
structures,
enlargement of the alveolar airspaces
distal
to the terminal bronchioles, and loss of elasticity of the
lung tissue without obvious F
brosis. Cigarette smoking
is the primary cause of the disease. Signs and symptoms
include
pursed-lip breathing
,
central cyanosis
,
± nger club-
bing
, and shortness of breath (
dyspnea
), hyperventila-
tion, “barrel chest,” and recurring respiratory infections.
Treatments include cessation of smoking, bronchodilating
agents, supplemental oxygen, and antibiotics for respira-
tory infections.
Hyaline
membrane
Inflammatory
cells
A
Enlargement
of the alveolar
airspaces
B
SYNOPSIS 11-1
Pathological and Clinical Terms for the Respiratory System
Hyaline membrane
: A histological feature of diffuse alveolar damage in early ARDS. It is a proteinaceous alveolar exudate
at the periphery of the alveolar space; also seen in hyaline membrane disease (RDS) of neonates.
Dyspnea
: Shortness of breath; may be due to a myriad of causes including congestive heart failure (pulmonary edema),
pulmonary embolus, asthma, and COPD.
Finger clubbing
: Also called “hypertrophic osteoarthropathy,” it represents enlargement of the distal aspect of the digits
due to proliferation of connective tissue and bone changes caused by many conditions including pulmonary diseases such
as COPD, infection, and malignancy.
Asthma
: A chronic infl ammatory disease of airways that manifests as paroxysmal contraction of airway smooth muscle
which causes narrowing of the airway lumens in response to exposure to a variety of triggers including allergens, infection,
and exercise; airway narrowing results in shortness of breath.
Squamous metaplasia
: A reversible change from mature cell types to squamous epithelium, such as occurs in ciliated pseu-
dostratiF ed columnar respiratory mucosa when exposed to environmental changes such as cigarette smoke.
previous page 233 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online next page 235 Dongmei Cui -  Atlas of Histology with Functional and Clinical Correlations 2011 read online Home Toggle text on/off